The F-35 is unstable by design and requires constant adjustments by the computer system to fly. So it is actually impossible to "just" turn the computer off and fly manually.
This is true for basically every fighter jet and stealth aircraft
"Modern" jet fighters, yes. I believe it started to be "hard" to fly manually with the F-16 and now it is completely impossible, but feel free to correct me.
F-16 was the first inherently unstable jet fighter, and the first one that featured a full fly-by-wire system with no backup. If you want a jet that is completely impossible to fly without a computer, F-16 is already one of them - there is nothing special with the F-35 about that.
Only on HN do people argue about an initial comment that they find nothing incorrect about, until they can find a little thing to be able to write "ahah you're wrong!"